[Plugin: Grunion Contact Form] Where can I push some bugfixes ?

Hi
I’m a webmaster and I use Grunion form one of my client’s website. I made some small bugfixes to remove the errors messages about undefined variables $extra_content_br and $comment_author_url_label. Where can I put them so that they will ship in the next version ?

Fabien

https://www.ads-software.com/extend/plugins/grunion-contact-form/